20123591 has 4 divisors (see below), whose sum is σ = 20378400. Its totient is φ = 19868784.

The previous prime is 20123581. The next prime is 20123611. The reversal of 20123591 is 19532102.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 19532102 = 2 ⋅9766051.

It is a cyclic number.

It is not a de Polignac number, because 20123591 - 2¹⁴ = 20107207 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (20123581) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 127286 + ... + 127443.

It is an arithmetic number, because the mean of its divisors is an integer number (5094600).

Almost surely, 2^20123591 is an apocalyptic number.

20123591 is a deficient number, since it is larger than the sum of its proper divisors (254809).

20123591 is an equidigital number, since it uses as much as digits as its factorization.

20123591 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 254808.

The product of its (nonzero) digits is 540, while the sum is 23.

The square root of 20123591 is about 4485.9325674825. The cubic root of 20123591 is about 271.9997431875. Note that the first 3 decimals are identical.

Adding to 20123591 its reverse (19532102), we get a palindrome (39655693).

The spelling of 20123591 in words is "twenty million, one hundred twenty-three thousand, five hundred ninety-one".